An ideal dosage regimen for many medications is that by which an acceptable therapeutic concentration of drug at the site(s) of action is attained immediately and is then maintained constant for the duration of the treatment. Providing dose size and frequency of administration are correct, therapeutic “steady-state” plasma concentrations of a drug can be achieved promptly and maintained by the repetitive administration of conventional peroral dosage forms. However, there are a number of potential limitations associated with conventional peroral dosage forms. These limitations have led pharmaceutical scientists to consider presenting therapeutically active molecules in “extended-release” preparations.
Oral ingestion is the traditionally preferred route of drug administration, providing a convenient method of effectively achieving both local and systemic effects. An ideal oral drug delivery system should steadily deliver a measurable and reproducible amount of drug to the target site over a prolonged period. Extended-release (ER) delivery systems provide a uniform concentration/amount of the drug at the absorption site and thus, after absorption, allow maintenance of plasma concentrations within a therapeutic range over an extended period of time, which can minimize side effects and also reduces the frequency of administration. ER dosage forms release drug slowly, so that plasma concentrations are maintained at a therapeutic level for a prolonged period of time. Typically, these products provide numerous benefits compared with immediate-release compositions, including greater effectiveness in the treatment of chronic conditions, reduced side effects, greater convenience, and higher levels of patient compliance due to a simplified dosing schedule. Because of the above advantages, such systems form a major segment of the drug delivery market.
Over the years many drug delivery systems have been developed with the aim of eliminating the cyclical changes in plasma drug concentration seen after the administration of a conventional delivery system. A variety of terms have been used to describe these systems: delayed release, repeat action, prolonged release, sustained release, extended release, controlled release and modified release. It is interesting to note that the USP considers that the terms controlled release, prolonged release, sustained release and extended-release are interchangeable.
There are at least three types of modified release pharmaceutical compositions in the pharmaceutical art; namely those that are delayed release, those that are extended release, and those that are both delayed and extended release. Delayed release pharmaceutical compositions are often designed to prevent drug release in the upper part of the gastrointestinal tract. Modified release coatings used to prepare this type of pharmaceutical composition are commonly called enteric coatings in the pharmaceutical art. Extended release pharmaceutical compositions are designed to extend drug release over a period of time, a result that is often achieved by the application of a sustained or controlled release coating.
Tramadol, which was first described in U.S. Pat. No. 3,652,589, is in a class of analgesic cycloalkanol-substituted phenol esters having a basic amine group in the cycloalkyl ring and having the chemical name trans-(±)-2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol. Tramadol is believed to produce an analgesic effect through a mechanism that is neither fully opioid-like nor non-opioid-like because clinical data suggest that tramadol lacks many of the typical side effects of opioid antagonists such as respiratory depression, constipation, tolerance and abuse liability but can produce hot flashes and sweating. Due to the combination of non-opioid and opioid activity, tramadol is a very unique analgesic and many attempts have been made to prepare oral compositions of the drug.
Conventional or immediate release preparations in the form of tablets, capsules, drops and suppositories containing tramadol, or more particularly its hydrochloride salt, have been commercially available for many years for use in the treatment of moderate to severe pain. For example, an immediate release oral composition of tramadol is commercially available in the United States, from Ortho-McNeil Pharmaceutical under the trade name ULTRAM® as tramadol hydrochloride tablets.
The clinical efficacy of immediate release tramadol preparations has been well established in numerous single dose and multiple dose studies, with 70% to 90% of patients obtaining satisfactory pain relief depending on the etiology of the pain. Immediate release tramadol preparations have demonstrated efficacy in obstetrical, gynecologic, orthopedic, abdominal and oral surgery. Immediate-release tramadol preparations have been studied in long-term clinical trials in patients with chronic pain of varying etiology, including low-back pain, osteoarthritis, cancer pain, neuropathic pain and orthopedic pain. The 53rd Edition of the Physician's Desk Reference, copyright 1999, p. 2255, states that peak plasma levels of tramadol for the ULTRAM® product occur at about 1.6 hours after a single oral dose (100 mg) and at about 2.3 hours after multiple oral dosing (100 mg q.i.d). Lintz et al. has demonstrated that a plasma concentration of total tramadol (sum of the (+) and (−) enantiomer) of 100 ng/ml is clinically effective in the treatment of mild to moderate pain (Lintz et al. Bioavailability of enteral tramadol formulations. 1st communication: capsules. Arzneimittelforschung 1986; 36: 1278-83). The short elimination half-life of tramadol necessitates dosing of patients with immediate-release tramadol preparations every 4-6 hours in order to maintain optimal levels of analgesia in chronic pain. The consequence of this multiple dosing schedule is the inevitable fluctuations of steady state concentrations of the drug in the plasma, and hence at the site(s) of action, leading to a patient being possibly over- or under medicated for periods of time if the values of Cmax and Cmin, rise or fall, respectively, beyond the therapeutic range. Another consequence of the multiple dosing schedule for ULTRAM® is that the concentration of tramadol in the plasma and hence at the site(s) of action of the drug fluctuates over successive dosing intervals, even when the so-called “steady-state” condition is achieved. Hence it is not possible to maintain a therapeutic concentration of drug, which remains constant at the site(s) of action for the duration of treatment. At best, the mean value of the maximum and minimum plasma concentrations associated with each successive dose remains constant for the period of drug treatment. Finally, because of the short-elimination half-life of tramadol the multiple dosing schedule for ULTRAM® must be adhered to in order to maintain steady-state plasma concentrations within the therapeutic range. For drugs such as tramadol, the maintenance of therapeutic plasma concentrations is particularly susceptible to the consequence of forgotten doses and the overnight no-dose period. Lack of patient compliance, which is more likely in the case of regimens requiring frequent administration of conventional dosage forms, can be an important reason for therapeutic inefficiency or failure.
Given the clinical efficacy of tramadol and the limitations of a conventional drug delivery system such as ULTRAM®, tramadol is an excellent candidate for an ER drug delivery system wherein the dosing schedule would be reduced to once-daily administration of the ER dosage from. An ER dosage form would be even more advantageous if it could reduce the adverse events or side effects often seen with immediate-release compositions of tramadol. Accordingly, there is a need in the art for an ER dosage form of tramadol exhibiting reduced adverse events or side effects compared to the currently marketed ULTRAM®.
Indeed, various attempts have been made to formulate tramadol into modified-release compositions. For example, such compositions purporting to control the release of tramadol within the gastrointestinal tract, with the purported result that tramadol is delivered at a specific predetermined rate have been described in several patents and patent applications.
U.S. Pat. Nos. 5,958,452, and 6,254,887 to Miller et al. describe a controlled release preparation of tramadol, wherein the tramadol is incorporated into a controlled release matrix. The references also state that the controlled release preparation may comprise a normal release matrix having a controlled release coating, but fail to describe or disclose how such a preparation is to be made. FIGS. 1 and 2 of the '887 reference show that the controlled release tramadol preparation when administered as a single dose releases tramadol without any delay or lag time, and there is no disclosure or teaching relating to making a controlled release tramadol preparation with a delay or lag time. It is known in the art that a relatively quick release of certain irritant drugs may increase the incidence and severity of localized gastrointestinal side effects. While the rate of release of tramadol from the composition described in the '887 reference is admittedly slower than that of the conventional release tramadol drop preparation Tramal®, the reference does not teach if the controlled release composition was able to reduce or at least equal the incidence of any adverse events compared to Tramal®. In fact, neither Miller reference provides any data on the adverse events or side effect profile of the claimed composition.
U.S. Pat. Nos. 5,672,360 and 5,478,577 disclose a method of treating pain in humans comprising orally administering on a once a day basis an oral sustained release dosage form of an opioid analgesic which upon single dose and multiple dose administration provides a time to maximum plasma concentration (Tmax) of said opioid in about 2 to 10 hours and a maximum plasma concentration (Cmax) which is more than twice the plasma level of said opioid at about 24 hours after administration of the dosage form and which dosage form provides effective treatment of pain for about 24 hours or more after administration to the patient.
U.S. Pat. Nos. 5,395,626, 5,474,786, and 5,645,858, all to Kotwal et al., disclose a multilayered controlled release pharmaceutical dosage form comprising a plurality of coated particles comprising a core containing tramadol, hydroxypropyl methylcellulose, polyethylene glycol and propylene glycol overcoated with a controlled release barrier comprising ethylcellulose and which is over coated at least once with a mixture of tramadol, hydroxypropyl methylcellulose, polyethylene glycol and propylene glycol, which is again overcoated with an additional controlled release barrier comprising ethylcellulose. A final outer layer may comprise tramadol intended for substantially immediate release. These references do not provide any comparative data of the performance of the composition taught therein to an immediate-release composition of tramadol, such as ULTRAM®, or to the controlled release compositions of Miller described above. The in vitro dissolution profiles of the Kotwal compositions appear to show a slight delay in the release of tramadol, however pharmacokinetic data have not been presented to determine the efficacy of these compositions nor have any data been presented on the incidence of any adverse events resulting from the administration of the compositions. As a result, it is not known whether the apparent slight delay in in vitro dissolution necessarily results in any delay in in vivo plasma levels. Accordingly, it is not known if the apparent slight in vitro delay in the extended release of the tramadol of the Kotwal compositions has any clinical significance.
U.S. Pat. No. 6,576,260 describes a sustained release formulation of tramadol comprising tramadol saccharinate coated with at least one sustained-release coating. The tramadol saccharinate is itself a poorly soluble salt of tramadol and contributes to the sustained release of the composition. Further retardation is achieved by a sustained release coating. In vivo performance of this formulation is not disclosed.
US Patent Publication No. 2003/0143270A1 discloses a once daily extended release composition containing tramadol. The composition comprises a core containing tramadol or its pharmaceutically acceptable salts, a water soluble insulating membrane separating the tramadol containing core from the controlled release membrane, and a controlled release membrane. The composition in vitro exhibits a biphasic dissolution profile. The composition purports to provide an effective blood concentration of about 24 hours with reduced peak concentrations. The composition provides effective tramadol levels within about 1 to 2 hours after a single administration of the composition where the time to peak tramadol content is at least 10 hours and the peak tramadol concentration is less than three times the concentration obtained after 24 hours of administration. The document does not disclose the side effect or adverse event profile of the composition in comparison to the immediate release formulation.
EP patent Application No. 1190712A1 describes a composition comprising a core containing tramadol or its pharmaceutically acceptable salts, a water soluble insulating membrane separating the tramadol containing core from the controlled release membrane, and a controlled release membrane. The water soluble insulating membrane between the core and the rate controlling releasing membrane reduces the differences of tramadol dissolution rates between batches. The composition provides a time to peak tramadol content of at least about 10 hours versus 2 hours as well as a significantly reduced Cmax in comparison to the immediate release composition. The document does not disclose the side effect or adverse event profile of the composition in comparison to the immediate release formulation.
U.S. Pat. No. 5,601,842 discloses a tablet containing tramadol and a matrixing agent with a viscosity between 3,000 and 150,000 mPa in a 2% aqueous solution at 20° C.
U.S. Pat. No. 5,811,126 discloses a controlled release pharmaceutical composition containing tramadol and comprising sodium alginate, C2 to C50 edible hydrocarbon derivative with melting point range from 25° C. to 90° C. and divalent salt to cross link the alginate. In vivo performance from these formulations is not available.
U.S. Pat. Nos. 5,639,476 and 5,580,578 disclose controlled release dosage forms containing a substrate containing tramadol, said substrate being coated with a plasticized aqueous dispersion of ammonio-methacrylate copolymer having low content of quaternary ammonium groups and a permeability enhancing pore former, said coating being cured for about 24 to about 60 hours to stabilize said formulation.
U.S. Pat. No. 5,955,104 discloses a delayed release tramadol formulation consisting of pellets in a water soluble capsule or in a tablet compressed from said pellets, each pellet having (a) a substantially inert core; (b) an active ingredient layer over the inert core and containing (i) tramadol particles, (ii) with a binder for adhering said tramadol particles over said inert core, and optionally (iii) a pharmaceutically acceptable, inner adjuvant; and (c) a delay coating for retarding the release of tramadol consisting principally of mixtures of ethylcellulose and shellac.
U.S. Pat. No. 5,849,240 describes a process for the manufacture of particles by the “melt-pelletization” process. Tramadol is one of the examples but the in vivo performance of such a formulation is not available.
U.S. Pat. No. 5,965,163 describes a solid dosage form comprising a plurality of particles including tramadol in a matrix, the matrix including a mixture of hydrophobic and hydrophilic fusible carriers having melting point from 35° C. to 150° C., which are produced by the method of “melt-pelletization”.
U.S. Pat. No. 5,958,482 describes a sustained release pharmaceutical formulation comprising an extruded blend of tramadol, and one or more hydrophobic fusible carriers having a melting point from about 30 to about 200° C., providing a sustained-release of said therapeutically active agent for a time period of from about 8 to about 24 hours, with a peak plasma level for about 2 to 8 hours.
U.S. Pat. No. 5,891,471 teaches tramadol pharmaceutical particles for once a day administration, which provides a time to peak plasma level of tramadol in about 2 to about 6 hours after administration, produced by a process of “melt-pelletization”.
U.S. Pat. No. 5,968,551 describes a sustained release oral analgesic form for once a day administration comprising a unit dose comprising a plurality of pharmaceutically acceptable matrices comprising an analgesically effective amount of tramadol and hydrophobic material, each of said matrices having a diameter of about 0.1 to 3 mm and having a therapeutic effect for about 24 hours or more after oral administration to a human patient. It also discloses a method of treating patients for moderate to severe pain with a once daily oral administration of a unit dose consisting of a plurality of inert pharmaceutically acceptable beads coated with an analgesically effective amount of an opioid and a sustained release coating. The beads have a diameter of 0.1 to 3 mm and provide effective blood levels of the opioid for about 24 hours with peak plasma levels of the opioid in vivo from about 3 to about 10 hours after administration.
U.S. Pat. No. 5,919,826 describes a sustained release tramadol composition providing a time to peak plasma level of about 2 to about 6 hours and produced by a process comprising high speed mixing of tramadol with a hydrophobic or hydrophilic carrier having a melting point from 35° C. to 150° C., and breaking down the agglomerates to give controlled release particles.
U.S. Pat. No. 6,376,550 is directed to a composition and method of treating migraine in which the composition consists essentially of pharmacologically effective amounts of both an antiemetic compound, such as metoclopramide, and tramadol. The reference does not teach, and in fact teaches away from, a composition comprising only tramadol as the pharmaceutically active agent.
U.S. Pat. No. 6,156,342 is directed to a controlled release dosage form for an analgesic that does not contain an expanding polymer and comprising a core containing an analgesic, preferably tramadol or its pharmaceutically acceptable derivatives and a semipermeable membrane coating the core. FIGS. 2 and 3 show a 4-hour delay before plasma tramadol levels are seen to rise. However, the formulation (P97540) cannot be clinically effective as the peak plasma concentration reached in both the fed and fasted state is about 40 ng/ml, which is significantly lower than the expected clinically effective plasma tramadol concentration of 100 ng/ml plasma tramadol reported by Lintz et al. There is no report in the reference to actual clinical or therapeutic effectiveness of the formulation.
International Patent Application No. PCT/CA2003/001638 (published as WO 2004/037222) describes a sustained release tramadol formulation for oral administration, which, upon initial administration of one dose, provides a mean plasma concentration of at least 100 ng/ml within 2 hours of administration and continues to provide a mean plasma concentration of at least 100 ng/ml for at least 22 hours after administration. The composition comprises tramadol and a matrix, wherein the components are associated in such a way that release of tramadol from the matrix is controlled. The matrix is a cross-linked high amylose starch known under the name Contramid®, which is described in U.S. Pat. No. 6,607,748. The matrix core is then coated with a physical mixture of polyvinyl acetate, polyvinylpyrrolidone and tramadol. The coat is formed by dry compression. No data have been provided to show whether the formulation exhibited a reduction in any adverse events compared to an immediate-release or other controlled-release formulation of tramadol.
The in vivo performance of a new oral sustained release dosage form of tramadol is described by Malonne et al. (Malonne et al. 2004. Pharmacokinetic evaluation of a new oral sustained release dosage of tramadol. 57(3): 270-278.). The reference does not teach the composition of the new sustained release dosage form, however, it allegedly provides better in vivo performance than an immediate release composition of tramadol in that it exhibits a significantly lower Cmax and longer Tmax compared to an immediate release tramadol composition. Food did not significantly modify any of the pharmacokinetic parameters assessed for the sustained release dosage form. However, the reference reports that the fluctuation and Cmin were similar for both the sustained release and immediate release compositions. Moreover, the sustained release composition did not appear to reduce the number of adverse events as the number of adverse events is reported to be similar to the immediate release composition.
Despite the many patents and patent applications describing sustained-release/controlled-release once-daily formulations of tramadol, it is noteworthy that as yet none of these compositions or formulations has been commercialized in the US. Given the clinical efficacy of tramadol and the limitations of a conventional drug delivery system such as ULTRAM® together with the fact that a controlled/extended/modified release dosage form of tramadol has yet to be commercially manufactured in the US, there remains a need in the art for a once daily extended release composition of tramadol which would also result in a reduction in the incidence and severity of untoward side-effects.